avoid creating html-entity AA at start-up - 10% speed up(!)

This is not even remotely funny creating this huge AA
at run-time took around 10% of the whole time to lex std.datetime
Redo hash table to avoid array append & GC lock/unlock

Also save hash to speed up in case of collisions & allow future re-hashing.
Merge pull request #29 from blackwhale/no-aa-please

avoid creating html-entity AA at start-up - 10% speed up(!)
Merge pull request #30 from blackwhale/tune-perf

Another tweak to string cache
Updated documentation and command line options based on things I'd like to eventually implement
Merged
first steps towards leaner common path in Lexer.advance
Accidentally a variable...
No longer needed
Merge pull request #31 from blackwhale/tune-lexer

First steps towards leaner common path in Lexer.advance
eliminating more of extra ops from the common path